Deception by Mirrors

Description

"Suppose the tumbler, a, to be filled with water, and placed beyond the principal focus of the concave mirror, and so managed as to be hid from eye c, by the screen b. The lamp by which the tumbler is illuminated must also be placed behind the screen, and near the tumbler, To a person placed at c, the tumbler with its contents will appear incerted at e, and suspended in the air." -Comstock 1850